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Tönn and its fellows Spotted Eagles

Tönn, the famous Spotted Eagle, is again overwintering in El Hondo (Alicante), eastern Spain. Tönn has been monitored aided by satellite tracking since 2008 from its breeding grounds in Estonia. Although its transmitter stopped some years ago, the bird is still holding it over its back – so it is still easy to identify – and since then returns every autumn to winter in El Hondo.

Tönn flying over El Hondo. Photo: Óscar Aldeguer

Interestingly, Tönn is actually a hybrid between a Lesser Spotted Eagle Aquila pomarina (father) and Greater Spotted Eagle Aquila clanga (mother). Both species are very close genetically and interbreeding is not rare along the hybrid zone, being a significant threat for the globally endangered Greater Spotted Eagle (more info here).

Genetic analyses and its external traits show that Tönn is more similar to its mother, therefore Tönn has been considered to be a putative Greater Spotted Eagle.

Tönn still holding the satellite transmitter on its back. Photo: Óscar Aldeguer

Additionaly, another presume adult Greater Spotted Eagle and a second-winter have been observed in the area this winter. Hence, this location is one of the most important sites in Spain for wintering Greater Spotted Eagles.

Other important sites in Spain for the species in winter include Ebro Delta, Doñana and the Strait of Gibraltar. For the latest site, this winter has been exceptionally good, especially for Lesser spotted eagles, recording over 10 different individuals and other hybrids including a tracked bird from Lithuania that even crossed The Strait in late November. Interestingly, in the winter 2014, other juvenil raised by the same pair, performed a more easterly migration route, crossing the Bosphorus and arriving to Kenya.

If you want to get more info, check Birding the Strait´s excellent post here.

Tönns transmitter stopped working in 2014. During this years (2016) breading season a transmittered GSE was observed by Eagle-Club members during fieldwork and after successfull breading period (1 flegged chick) he was caught. They identified the bird as Tönn, gave him a new transmitter and a plastic ring.
So now it is possible to follow his route on the birdingmap as before. Thanks to this and a tipp by Eagle-Club member Urmas Sellis my friend and I were able to see the bird during a short overnight visit near Munich/Bavaria where we live (1st observation in Germany!). Our picture showed the bird with light patches on the upper wingside, and this picture is nearly similar to some other earlier pictures made by other people during wintering times at El Hondo.
I reported the observation to Urmas (who identified Tönn on our foto). And we reported to ornitho.de and our German Rarity Commission, but because your information about the bird being hybride or not I asked Urmas Sellis for more information. And he told us that “by our DNA data Tõnn is pure GSE”.